Fuel supply module diesel and gasoline for different automobiles
Your Fuel pump worn out? » Read more about common malfunctions • Repair • Replacement manual
Supplying the engine under pressure: the fuel pump
The flow of fuel between tank and engine is actuated by the fuel pump, adapting the exact measure of fuel or diesel required by the engine.
In the old days, fuel was drawn from the tank by vacuum, the pump being situated next to the engine and driven mechanically by cogwheels or belts. Mechanical feeding pumps are too feeble and not sufficiently precise for modern engines. Nowadays, diesel as well as petrol pumps are driven by electric power.
Fuel pump types
The technical layout of the fuel pump depends first and foremost on the type of fuel. The texture of petrol and diesel is very different. The viscous and oily constitution of diesel requires a displacement pump which is generally located in the tank. This location complicates its replacement, although it ensures permanent and optimal lubrication as well as cooling. Consequently, this type of pump enjoys a long life span. The so-called flow pump is common in petrol cars. Different construction types apply. Mostly these are roller vane pumps, flywheel pumps, rotary pumps or similar modules of simple construction. The petrol pump can also be found within the tank, although it is often located separately.
Life span of a fuel pump
A fuel pump is built to last ca. 10.000 operating hours. Calculated in mileage this equals ca. 150.000 km, practically a normal car's life span. In newer cars with less than 100.000 kms on the clock a fuel pump failure is therefore rather unlikely, though if it happens it is likely to announce itself in time.
Defect of the fuel pump
The fuel pump is a module consisting of electric motor, housing and pumping unit. As in all electric motors, the carbon brushes of the petrol pump are subject to wear. Also, bearings can jam or the rotor and stator coils can burn out. The pump component is mostly made of plastic. Parts can break off and block the pump. A fuel pump is therefore generally not repaired but replaced.
Fuel pump defects announce themselves as follows:
- starting difficulties
- increased fuel consumption
- ignition failures during driving
- Sudden failure of the car.
Please note: starting difficulties and increased fuel consumption can be the result of an old air filter. The ignition failures can be caused by a defective ignition cable. A sudden failure of the car can be due to a corroded earth cable. Therefore it is important to exclude the obvious causes first. Only when operating the car fails to improve after replacement of air filter, ignition and earth cable, deeper investigation is necessary. One symptom is unmistakable. Normally, the fuel pump gives off a soft buzz when the ignition key is turned. If this buzz does not occur and the car refuses to start, the culprit has been identified.
Costs for a fuel pump
The price of a new fuel pump strongly depends on the type of car in which it is used. In principle, fuel pumps are very type-specific and therefore difficult to replace by a used part. Prices start at 40 EUR (± £35). This applies to older cars like e.g. a Golf 3. In modern cars with higher engine performance a new fuel pump can easily cross the 1,000 EUR (± £900) mark. Replacement costs add to the purchase price. It strongly depends on the car type and the skill of the mechanic how quickly a defective fuel pump can be replaced. In many models this takes no more than two hours' work. Some cars require replacing the entire tank on occasion of which the rear axle has to be disassembled. All in all the replacement of a fuel pump is one of the moderately difficult repairs, which can be performed DIY with a bit of practice.